There is a trend in the magnetic recording disk industry toward the fabrication of ever smaller disks. Disks with diameters as large as 355 mm. used to represent a large portion of the industry's production, but now manufacturers are producing disks as small as 48 or 34 mm. There are several reasons for this trend toward smaller disks. One reason is that smaller disks provide better data access times. A disk with a smaller diameter decreases the distance that a read/write head has to travel to access data. Therefore, the head reaches the data sooner and access time is reduced. Improved access time is also achieved with smaller disks because they can accommodate smaller and lighter actuator arms. Less massive actuator arms result in faster acceleration of the read/write head and faster data access.
The trend toward smaller disks is also driven by the demand for smaller and lighter portable computers. Smaller disks are well suited for applications such as notebook computers where weight and power consumption are critical design factors. As the demand for computer portability increases, so will the demand for ever smaller disks.
The ability of manufacturers to market these smaller disks is, in large part, a result of improvements in the magnetic coatings on the disks. Improved magnetic coatings now allow manufacturers to achieve much higher areal recording densities than previously available. That is, more information can now be stored on a given surface area of a disk. This improvement makes it possible for useful amounts of data to be stored on smaller disks.
The increased demand for smaller disks has created several problems for modern disk manufacturing facilities. One of these is the limitation on manufacturing throughput associated with the fabrication of small disks. As will become apparent from the following discussion, the throughput of many of the processes involved in disk fabrication declines as the diameter of the manufactured disk is reduced.
The fabrication of magnetic disks requires several thin films to be formed on the top and bottom surfaces of the disk. The conventional method of creating these thin films is to sputter deposit them on the surfaces of the disk. Two general categories of sputtering tools can be used to apply these films. The first, and most commonly used, category of tools are the single-disk tools, in which a single thin film layer is sputtered onto a single disk. The disk is then transferred to other single-disk sputtering tools for the deposition of subsequent layers. The second category of sputtering tools are known as pass-through tools or inline systems. In this type of tool, several disks are mounted on a pallet and passed through several coupled sputtering chambers while the required thin films are deposited.
The fabrication of disks using single-disk tools can be very time consuming. For each disk to be processed, several steps must occur. The disk must be placed in the sputtering tool; a vacuum must be created in the sputtering chamber; the disk must be kept in the chamber long enough for the required film thickness to be sputter-deposited; and finally, the disk must be removed from the chamber. This type of processing limits the throughput of the sputtering operation since only a single disk may be processed at a time. The processing time required is essentially the same regardless of the size of the disk being processed. Therefore, if throughput is measured in terms of the square centimeters of storage area created per hour, it is clear that the fabrication of smaller disks causes a decrease in the throughput of a disk manufacturing facility.
One way of addressing the throughput problems associated with single-disk tools is to utilize a pass-through system like those previously described. However, such an approach leads to several difficulties. Problems associated with this approach include the difficulty of suspending several disks in a pallet while both sides of the disk are exposed to the sputtering operation. Often the pallet shadows the disks and results in a nonuniform coating on the disk. In addition, the pallet itself becomes coated with the material that is being sputter deposited. This causes the pallet to become a source of contamination which must be frequently cleaned. The cleaning process is time consuming, costly, and can cause excessive tool downtime.
The present invention solves the above described throughput problems of the single-disk tools while avoiding the difficulties associated with the pass-through systems. In addition, the present invention can be adapted for use in a pass-through tool while avoiding the above described problems typically associated with such tools.